In Drosophila tissue culture cell lines, the four small heat shock genes are induced by both high temperature shock and by treatment with physiological doses of the steroid hormone, ecdysterone. The long term objective of the research is to understand the molecular events involved in the regulation of this gene cluster, in response to the two different stimuli. The specific aim of current research is to develop a transient expression system, using Drosophila cells. Cloned Drosophila heat shock genes will be introduced into cells by transfection or liposome fusion. Their constitutive and regulated expression will be determined. Once a functional assay for the regulation of cloned genes is developed, modifications of the DNA sequence near the 5 feet ends of the genes will be introduced in vitro, and the effects of these modifications on regulated gene expression will be determined. The objective is to determine which of the DNA sequences flanking the structural gene are involved in regulated expression.